1. Technical Field
The present invention relates to an liquid ejecting head of an ink jet type recording head and the like, and in particular, to an liquid ejecting head for introducing a liquid stored in a liquid storage member to a pressure chamber via a liquid introducing needle and ejecting the liquid introduced into the pressure chamber from a nozzle opening as a liquid drop.
2. Related Art
As for a liquid ejection head for ejecting a liquid from a nozzle opening as a liquid drop by generating pressure fluctuation to a liquid in a pressure chamber, there are included, for example, an ink jet type recording head (hereinafter, simply referred to as a recording head) for used in an image recording apparatus such as an ink jet type recording apparatus (printer), a color material ejecting head for use in color filter manufacture such as a liquid crystal display, an electrode material ejecting head for use in electrode formation such as an organic EL (Electro luminescence) display and an FED (field emission display), a living organic matter ejecting head for use in bio chip (biochemical element) manufacture, and the like.
For example, in the above recording head, an ink in an ink cartridge is introduced into a pressure chamber side of the recording head via an introducing through hole opened at a distal end side of an ink introducing needle by introducing the ink introducing needle which is a type of a liquid introducing needle into the ink cartridge as a liquid storage member in which an ink in the form of liquid is enclosed. In addition, a structure has also been proposed in which the ink cartridge disposed at printer main body side and the ink introducing needle of the recording head are coupled with an ink tube and the ink in the ink cartridge is send into the recording head by a pump or the like.
In the recording head having the above structure, it is ideal that an ink flow path (liquid flow path) from the ink introducing needle to the nozzle openings of the recording head is filled with ink. However, it is difficult to completely prevent that bubbles are intruded into the ink flow path when, for example, ink is filled into the recording head (initial filling) or the like. The bubble intruded into the ink flow path is grown and enlarged with passage of time and when the bubble excessively grown is moved to the pressure chamber side by passing through a filter disposed in the mid-course of the ink flow path by the flow of the ink, there is a risk in that a disadvantage such as pressure loss caused when the bubble absorbs pressure fluctuation during ejecting operation, and shortage of supply of the ink caused when the bubble closes the flow path may be invited.
As a method for preventing such a disadvantage caused by a bubble, there is included a method for enhancing bubble discharging efficiency so that the bubble is prevented from remaining in the ink flow path as much as possible. As the method, for example, in JP-A-11-078046, a structure has been proposed in which a bubble guiding groove is provided on the inner circumference surface of the ink introducing needle near a filter (filter attached member) and the bubble in the ink flow path is positively introduced to the downstream side by the bubble introducing groove. At the same time, in JP-A-11-227228, a structure has been proposed in which the flow of the ink during initial filling is controlled by forming an ink introducing path on the inner circumference surface of the filter chamber formed at the proximal side of the ink introducing needle to improve bubble discharging property by pushing out the bubble to the downstream side by the ink.
Further, as a method different from the above described method, a conical shape bubble chamber (enlarged diameter portion) may be provided at the proximal sided of the ink introducing needle to positively store and keep the bubble in the bubble chamber, thereby preventing that the bubble is moved to the downstream side by passing through the filter by an ink flow velocity during normal recording operation (ejecting operation of ink drop). As for the example, in JP-A-2005-186494, a structure has been proposed in which a bubble interference member is to be disposed in the bubble chamber of the ink introducing needle to prevent that the bubble is moved to the filter side by the bubble interference member during recording operation.
However, a space of a portion functioning as the bubble chamber is not widely assured in each of the structures. Accordingly, when bubble is grown inside of the ink introducing needle, it is required to frequently perform cleaning operation for forcibly discharging ink and bubbles in order to prevent the ink flow path and filter is closed by the bubble. As a result, there was a problem in that ink is uselessly consumed.
In addition, in the case of the conical shape bubble chamber, when the size is to be enlarged in order to obtain a large inner space, the ink introducing needle is inevitably widen in the longitudinal and horizontal directions. This enlarges disposition intervals of the ink introducing needles. As a result, there arises an adverse effect such as a difficulty of downsizing the recording head.